1. Field of the Invention
This specification relates to a mold cased circuit breaker capable of fast extinguishing arc, which is generated when a movable contactor is separated from a stationary contactor due to a fault current, by segmenting and cooling the generated arc and discharging arc pressure to the outside.
2. Background of the Invention
Generally, a mold cased circuit breaker is an electric protection apparatus, which is installed in an electric circuit to protect the circuit by preventing or minimizing damages on load equipment and lines due to fault currents (e.g., overload, short-circuit, etc.).
The circuit breaker typically includes a movable contactor, a stationary contactor, an arc-extinguishing device and the like. Upon occurrence of a fault current, the movable contactor is separated from the stationary contactor to trip a circuit and the circuit is protected accordingly. Here, when the movable contactor is separated from the stationary contactor, dielectric insulation in air is caused due to a current, thereby generating hot plasma arc state. Furthermore, gas is generated and accordingly arc pressure is generated. The thusly generated arc is segmented and cooled to be discharged outside, and a device performing such function is an arc-extinguishing device or an arc chamber.
The arc-extinguishing device generally has a structure that a plurality of grids are arranged in parallel. The grids absorb arc generated during tripping, thereby extinguishing the arc. Besides, various debris generated due to adjacent components being melted are adhered onto the grids, thus to reduce pressure within the circuit breaker, decrease erroneous operations of the circuit breaker, and increase an interruption capability.
FIG. 1 shows a type of a mold cased circuit breaker according to the related art. As shown in FIG. 1, the mold cased circuit breaker includes a main body having a front base 10, a rear base 20 and a cover 30 all for insulation from the exterior, a movable contactor 50, a stationary contactor 60, an arc-extinguishing unit 70, a switching mechanism 40 for mechanically switching a circuit on or off and the like.
FIG. 2 shows the related art arc-extinguishing unit 70 in more detail. As shown in FIG. 2, the arc-extinguishing unit 70, which is typically called an arc chamber, includes a pair of side plates 71, and grids 72 arranged in parallel within a space between the side plates with preset intervals. The arc-extinguishing unit 70 is positioned within the main body of the mold cased circuit breaker.
FIG. 2 shows a state that the movable contactor is separated from the stationary contactor. As shown in FIG. 2, the arc-extinguishing unit 70 is present in the space formed within the main body of the circuit breaker. The movable contactor 50 is rotated by the switching mechanism 40 to be separated from the stationary contactor 60. The movable contactor 50 then moves along a plurality of grids arranged in the arc-extinguishing unit 70 so as to extinguish arc. Debris generated during the separation is adhered on the grids of the arc-extinguishing unit 70 or the like.
However, such debris may be adhered on the movable contactor 50 or the stationary contactor 60 without entirely being adhered on the grids. Furthermore, the debris may be spread into the main body of the circuit breaker to thereby affect other components of the circuit breaker including the switching mechanism 40. The affection by the debris may cause an erroneous operation of the switching mechanism 40 of the circuit or interrupt the circuit, thereby lowering characteristics of the circuit.
Therefore, to improve the performance of the mold cased circuit breaker, a technique for effectively adhering such debris within the arc-extinguishing unit should be considered.